To predict the customer's acceptance of a mobile phone's performance and to predict the quality of the phone's design, actual use testing is required. Using tests is a valuable tool and this article will show you how to do this type of testing.
UMA/GAN is a cellular network (such as GERAN--GSM/EDGE Radio Access Network) and IP access network that allows mobile phones to transmit voice, data, voice and data, or neither voice nor data. A system that seamlessly switches between (eg, wireless LAN). As a milestone in the development of network convergence, UMA/GAN enables mobile phone users to enjoy the services provided by fixed broadband networks. UMA/GAN was originally called the Unlicensed Mobile Access (UMA) network, and was later renamed the General Access Network (GAN) by 3GPP. These two technologies are collectively referred to as GAN1.
The system architecture and protocols of GAN are described in 3GPP Technical Specifications 43.318 and 44.3182, 3. A mobile phone must be tested to meet the requirements of these standards before it can be placed on the market. But before that, mobile developers have many opportunities to test the consistency of their GAN products. Early verification of the phone's ability to process data and voice will greatly increase the chances that the product will successfully pass the conformance test.
Even for relatively mature technologies like GAN, designers can still differentiate their products by offering unique performance. WLAN is a technology that has been widely used in mobile phones. It can be used for both VoIP and data modems. One of the key factors affecting the use of GAN is the seamless handover between the IP network and the cellular network, which is a feature that the WLAN solution alone cannot provide.
Network componentThe GAN system also adds a new architectural component to the GERAN/UTRAN network: the GAN Controller, or GANC for short. GANC is functionally equivalent to a Base Station Controller (BSC) in a typical GERAN network. However, unlike the BSC, the front end of the GANC is connected to the IP access network, and the GAN-specific protocol is used to communicate with the mobile phone through this interface (referred to as the uplink interface). To ensure that signaling and user data can be transmitted between the handset and the core network, the GANC is also responsible for translating the messages of the upstream interface into the existing BSC/Core Network Interface Protocol (BSSAP/BSSGP protocol in the case of GSM).
Only dual-mode phones can enjoy the GAN service, which means that the phone must be aware when the user roams into or out of the Bluetooth or Wi-Fi network to switch between GERAN/UTRAN mode and GAN mode. Moreover, the handset must also establish an IPSec (Internet Protocol Privacy)-based VPN tunnel between itself and the serving GANC through a GAN-compatible Intermediate Security Gateway (SEGW). The data, voice and signaling services that are the basis of the mobile service can be properly protected and transmitted through this tunnel.
How to establish a GAN connectionWhen performing GAN network deployment, several GANCs are usually required to share the tasks of providing GAN services while ensuring load balancing. Each GANC in the network shall serve at least one of the following logical entities: a configuration GANC (P-GANC), a default GANC (D-GANC), or a service GANC (S-GANC).
If a mobile subscriber has a mobile phone with a GAN function, the GAN function of the mobile phone can only be used when the mobile phone is within the coverage of the license-free wireless network to which it can be connected. When the phone first tries to establish a connection, it needs to identify the default GANC (D-GANC). Therefore, it initiates the discovery process to receive information about the D-GANC and use it during the registration process.
To obtain the D-GANC's address and its associated Security Gateway (SEGW) information, the handset connects to the configured GANC in its Home Public Land Mobile Network (HPLMN) via the associated SEGW of the P-GANC. A P-GANC address and associated SEGW should be stored in a mobile phone with a fully qualified domain name (FQDN) or IP address. Otherwise, the mobile phone can also obtain the FQDN based on the information on the (U)SIM card. The addressing requirements are described in detail in 3GPP TS 23.0035.
Next, the handset will establish a secure channel with the D-GANC's SEGW and attempt to register with the D-GANC. If the D-GANC accepts the registration, it will become the S-GANC of this connection, otherwise it will direct the registration request of the mobile phone to another S-GANC. A mobile phone can be continuously registered in an S-GANC indefinitely even if it is not working in the GAN mode, and enjoys the GERAN/UTRAN service so that voice and data can be switched to the GAN network in time when needed. Once the mobile phone explicitly switches to the GAN network or the user decides to switch to use GAN, the current location information of the mobile phone user (the information is stored on the core network) will be refreshed by the mobile phone, and then the voice/data and signaling traffic will be Sent to the phone via the GANC instead of the cellular network.
The role of the security gatewayA key part of the GAN system is the Security Gateway (SEGW), which provides a secure connection between the mobile phone and the carrier network at the other end of the "unsecure" IP access network.
In a typical GAN ​​deployment, the SEGW is responsible for establishing and maintaining a secure (encrypted by IPSec/IKEv2 standard) connection between the handset and the core mobile network where the GANC is located. After establishing the GAN connection, the mobile phone must authenticate the security gateway with the signed public key security certificate. This is to ensure that when users use the GAN through the public IP access network, they will not be "spoofed" to other malicious networks without their knowledge.
The SEGW can also act as a communication intermediary between the handset and the connected billing, authentication and authorization server (AAA), authenticating users and allowing them to use the GAN services provided by the network. The AAA server authenticates the decision based on the result of the request/response password sent to the handset, and forces both the handset and the network to verify the shared private "k" value on the user's SIM or USIM card and the network to which the AAA server is connected. Home location register information. In addition to authenticating the handset and the network, the results of the authentication algorithm can also be used to derive the key information required by both parties to encrypt the IPSec connection between the handset and the SEGW.
The authentication protocol between the mobile phone and the AAA server is different in 2G and 3G networks. The authentication protocols used by 2G and 3G networks are based on existing 2G and 3G authentication technologies, but have been greatly improved to enhance the protection of often more vulnerable IP access networks. The 2G network uses an extended authentication protocol for the Subscriber Identity Module (EAP-SIM), while the 3G network uses an extended authentication protocol for UMTS authentication and key negotiation (EAP-AKA).
When the test conditions do not allow the GAN security function in the mobile phone to be disabled, the SEGW and AAA server components with certain IPSec and EAP functions must be deployed in the test system so that the mobile phone can connect to the GAN network and use the GAN service.
Test considerationsWhen trying to verify the design parameters of a GAN phone, the design engineer needs to answer the following questions. First, which parameters must be tested when testing the conformance with the standard? Second, which actual use case tests best indicate whether the phone design meets the target? Finally, when you want to reduce duplication of work and unnecessary repetitive testing during the design process, when is the best time to test?
Just like a pure cellular network, in the GAN network, call setup, call termination, and handover functions are most likely to be weaknesses in the system, increasing the chances of service failure and user dissatisfaction. In order to thoroughly test these features, it is best for the design engineer to have a test platform with test capabilities and preferably close to other members of the design team. This will enable the design team to make efficient decisions based on test results.
The GAN system introduces a new signaling procedure, an access layer technology that is adopted by many existing upper layer functions. 3GPP has specified a number of conformance test projects in 3GPP TS 51.010-14, and GAN-enabled handsets must undergo these tests before they can be launched. Although these test specifications give considerable attention to GAN-specific new program testing, there is little involvement in the use and user experience of existing cellular communication technologies deployed on GAN. Therefore, design engineers can choose from a number of work scenarios to test, including:
* GAN found the success or failure of the program
* Success or failure of the GAN registration program including register updates
* Initial mobile station mode selection between GAN and GERAN/UTRAN operations
* Mobile originated (MO) and mobile terminated (MT) GAN voice calls
* GAN-based data connections and end-user experience with devices that use these underlying connections
* GAN-based dual mode transmission (DTM) or SS (UTRAN) connection
* Transfer GSM-based MO and MT point-to-point SMS messages via GAN
* Transfer GPRS-based MO and MT point-to-point SMS messages via GAN
* All applicable inbound and outbound cellular scenarios include: roaming in (from G/U to GAN network), roaming out (from GAN to G/U), switching in (from G/U to GAN), switching out (from GAN To G/U), cellular change commands (from G/U to GAN), switch in/out during DTM or SS connection (from GAN to G/U and from G/U to GAN)
GAN test configurationUsing a dedicated wireless communication test suite such as the Agilent 8960, you can simulate the different scenarios required for GAN functional testing in a controlled and repeatable manner. This type of testing is important throughout the development cycle of the GAN handset, from the early design phase through to system integration and verification, simulation and field testing, interoperability testing, and compliance testing.
Figure 1 shows a configuration of a GAN handset functional test in which an application running on a PC is used to mimic the GANC.
Figure 1: GANC simulation with software.
In this configuration, any device that can connect to the phone and obtain an IP address can provide an IP network connection. An ordinary commercial WLAN access point is used in Figure 2.
Figure 2: GAN test configuration using the Agilent 8960 test suite and commercial WLAN access points.
Other test considerationsIn addition to verifying that a phone's performance meets the GAN standard, design engineers should also consider test items that are not covered by the standard but are relevant to everyday use. Here are three examples of usage tests, which show that these tests are useful for predicting the actual performance of a mobile phone.
Current consumption analysisUnlike the cellular communication standard, the WLAN standard does not take into account the battery capacity of the user equipment, so its power consumption may be large. A single-mode GSM phone that uses battery even when it is running in standby mode
Unlike the cellular communication standard, the WLAN standard does not take into account the battery capacity of the user equipment, so its power consumption may be large. A single-mode GSM phone, even if it is running in standby state, its battery life may be five times that of a mobile phone battery running in WLAN mode. If you count the talk time again, the difference between the two will be even greater. Because a GAN-enabled handset must monitor both GERAN, UTRAN, and GAN networks, battery life should be a major consideration in design.
A comprehensive analysis can be used to assess the impact of current consumption at critical application points (eg, during packet data transmission as shown in Figure 3). The vertical axis of Fig. 3 corresponds to a change in time, and the horizontal axis corresponds to a change in amplitude.
Figure 3: Measurement and analysis of battery current consumption using the 14565B CCDF.
Voice qualityVoice over GAN is very similar to Voice over IP (VoIP) in terms of using IP packets as the underlying voice data. In the GAN, the IP packet contains GSM encoded and encapsulated voice information. The difference between Voice over GAN and GERAN/UTRAN voice calls is mainly in the decision of codec selection. In GAN, the choice of codec is limited by the percentage of lost packets, not the power level perceived by the mobile phone or the relative of carrier and interference. Level decision.
Although the GAN standard has not yet enforced receiver sensitivity testing for codec rate changes or any hysteresis associated with the number of lost packets, these factors may significantly affect user-perceivable handset performance because of AMR editing. Even if the decoder only changes slightly, sensitive users may be aware of it. The voice quality test is a great help in assessing how a GAN phone design can solve these problems (see Figure 4).
Figure 4: Relationship between voice quality and packet loss rate and lag.
Data throughput testThe third and most basic type of usage test is to evaluate end-to-end data throughput and find response delays that may affect the user experience. The design engineer must simulate multiple usage scenarios and measure the end-to-end IP data rate on the WLAN connection and any changes that occur when the call is handed off (eg, switched to the GERAN serving cell) and switched back.
This is very important because the theoretically achievable data rate when using a typical GAN ​​access network (eg wireless LAN) will increase geometrically compared to the slower data rate using GERAN/UTRAN networks, see Figure 5. .
Figure 5: Traffic analysis from GAN to GERAN to GAN conversion.
Summary of this articleThere are many factors to consider when validating a design implementation prior to conformance testing. Although the list of test scenarios mentioned in this article is not comprehensive enough, it still provides a very reliable basis for understanding the performance of mobile phones. Performing these tests in a suite that mimics the GAN system can help engineers assess the impact of various decisions, minimizing the number of iterations that may be required during the design cycle. This approach greatly saves designers time, effort and design costs. Similarly, the actual use test also allows engineers to predict the customer's acceptable performance on the phone, thus predicting the quality of the phone design. Therefore, the use of testing is a very valuable tool that should be included in the design engineer's toolbox in order to increase the chances of successful commercial use of the product.
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